The drug discovery process is currently undergoing a fundamental revolution as it embraces `functional genomics`, that is, high throughput genome- or gene-based biology. This approach is rapidly superceding earlier approaches based on `positional cloning`. A phenotype, that is a biological function or genetic disease, would be identified and this would then be tracked back to the responsible gene, based on its genetic map position.
Functional genomics relies heavily on the various tools of bioinformatics to identify gene sequences of potential interest from the many molecular biology databases now available. There is a continuing need to identify and characterise further genes and their related polypeptides/proteins, as targets for drug discovery.
Multi-specific drug transporters are present in cells having a barrier function such as intestinal epithelial and brain microvessel endothelial cells. Other tissues, for example, liver and kidney, also contain multi-specific transporters that can mediate the excretion of drugs and metabolites. Recently, it has been recognized that transporters encoded by genes such as mdr1 contribute to poor intestinal absorption and brain penetration of drugs. Information gained from using multi-specific transporters such as the mdr1 gene product in cell based, membrane based, binding or other assays could enhance drug formulation, selection of formulation excipients, and compound design.